Air bag sensor module fastening device

ABSTRACT

An air bag sensor module fastening device for a vehicle is provided includes a vehicle mounting structure having an internally threaded member. A sensor is secured to a base for sensing vibrations caused by a crash of the vehicle. The base has an aperture extending therethrough that is aligned with the internally threaded member. The aperture includes a retaining portion. A fastener for securing the base to the vehicle mounting structure has a shaft with a head and a threaded portion opposite the head. The threaded portion is temporarily retained within the retaining portion in a shipping position. The threaded portion has a minor diameter and the shaft portion has a shaft diameter less than the minor diameter. As a result, the shaft will not be in an interference fit relationship with the retaining portion so that the compressive load of the fastener alone secures the base to the vehicle mounting structure. The threaded portion is disposed outside of the retaining portion in an installed position in which the threaded portion is received in the internally threaded member to secure the base to the vehicle mounting structure. In this manner, the threaded portion will engage only the internally threaded member so that the base is secured to the vehicle mounting structure by the compressive load of the fastener alone.

[0001] This application is a Continuation of U.S. patent applicationSer. No. 09/592,080 filed on Jun. 12, 2000.

BACKGROUND OF THE INVENTION

[0002] This invention relates to air bag sensor modules that are securedto the vehicle structure for transmission of crash pulses, and morespecifically, the invention relates to a fastening device for securingthe module to the vehicle structure.

[0003] Air bag sensor modules include a crash sensor and are mounted onthe vehicle structure in a manner to transmit crash information from thevehicle structure to the crash sensor. Diagnostic circuits evaluate thecrash information and discriminate between a fire and a no firecondition. To this end, the air bag sensor module is mounted on thevehicle such that the crash sensor will be subject to forces thatindicate a crash condition. For example, the crash sensor usuallycomprises an accelerometer and the air bag module is rigidly coupled toa portion of the vehicle such that deceleration indicative of a crashcondition is transmitted to the crash sensor. When a crash conditionrequiring air bag deployment is detected, the controller associated withthe air bag module sends a signal to ignite an air bag deploymentdevice.

[0004] To ensure that the forces are properly transmitted from thevehicle structure to the crash sensor, the module must be securelyfastened to the vehicle structure. Typically, the manufacturer of themodule supplies the module to the vehicle manufacture, which providesthe fastening elements used to secure the module to the vehiclestructure and installs the module onto the vehicle structure.Preferably, the fastening elements are secured to the vehicle structureonly under the compressive load of a threaded fastener to ensure optimalcrash pulse transmission. By having the vehicle manufacturer supply thenecessary fastening elements, variables are introduced that maycompromise proper installation of the module and inhibit crash pulsetransmission. For example, the threads of the fastener may engage boththe module and the vehicle structure so that the module is not securedto the vehicle structure by compressive load alone. Additionally, theshaft of the fastener may be in an interference fit relationship with amodule mounting hole, again preventing the module from being secured tothe vehicle structure by compressive load alone. Therefore what isneeded is a fastening device which secures the module to the vehiclestructure only by the compressive load of the fasteners to ensureoptimal crash pulse transmission.

SUMMARY OF THE INVENTION AND ADVANTAGES

[0005] The present invention provides an air bag sensor module fasteningdevice for a vehicle. The fastening device includes a vehicle mountingstructure having an internally threaded member. A sensor is secured to abase for sensing vibrations caused by a crash of the vehicle. The basehas an aperture extending therethrough that is aligned with theinternally threaded member. The aperture includes a retaining portion. Afastener for securing the base to the vehicle mounting structure has ashaft with a head and a threaded portion opposite the head.

[0006] The threaded portion is temporarily retained within the retainingportion in a shipping position. The threaded portion has a minordiameter and the shaft portion has a shaft diameter less than the minordiameter. As a result, the shaft will not be in an interference fitrelationship with the retaining portion so that the compressive load ofthe fastener alone secures the base to the vehicle mounting structure.The threaded portion is disposed outside of the retaining portion in aninstalled position in which the threaded portion is received in theinternally threaded member to secure the base to the vehicle mountingstructure. In this manner, the threaded portion will engage only theinternally threaded member so that the base is secured to the vehiclemounting structure by the compressive load of the fastener alone.

[0007] Accordingly, the above invention provides a fastening devicewhich secures the module to the vehicle structure only by thecompressive load of the fasteners to ensure optimal crash pulsetransmission.

BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Other advantages of the present invention can be understood byreference to the following detailed description when considered inconnection with the accompanying drawings wherein:

[0009]FIG. 1 is a partial cross-sectional side view of an air bag sensormodule of the present invention fastening device with a fastener inshipping and installed positions;

[0010]FIG. 2 is side view of the fastener of the present invention; and

[0011]FIG. 3 is an enlarged partial cross-sectional view of the fastenerin a transient position preceding the installed position.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0012] An air bag sensor module 10 for a vehicle is shown in FIG. 1. Themodule 10 includes a fastening device 12 that has a vehicle mountingstructure 14 with an internally threaded member 16. As shown in FIGS. 1and 3, the internally threaded member 16 may be a nut that is secured toone side of the mounting structure 14 and aligned with a hole 18 in thestructure 14. The internally threaded member 16 may also be integrallyformed with the mounting structure such as a hole through the mountingstructure 14 that specially adapted to receive and retain a fastener.The module 10 has a base 20 with a sensor 22 secured thereto for sensingvibrations caused by a crash of the vehicle. The sensor 22 and base 20may be formed as single unit or as separate components. Typically, thebase 20 includes a protrusion 24 that is received within a locating hole26 in the mounting structure 14 for positioning the module 10 relativeto the structure 14. The base 20 may be manufactured from plastic ormetal.

[0013] The base 20 has an aperture 30, typically three or four,extending through the base 20 and positioned to align with theinternally threaded members 16. The aperture 30 includes a retainingportion 32 and preferably a pocket 34 adjacent to the retaining portion32. Fasteners 36 are received within the apertures 30 for securing thebase 20 to the vehicle mounting structure 14. Referring to FIG. 2, thefastener 36 has a shaft 38 with a head 40 and a threaded portion 42opposite the head 40. Threads 44 on the threaded portion 42 are enlargedin the Figure for clarity. The shaft 38 has a shaft diameter X, and thethreaded portion 42 has a minor diameter Y defined by the root or valleyof the threads 44.

[0014] The fastener 36 has a shipping position (shown on the left sideof FIG. 1), an installed position (shown on the right side of FIG. 1),and a transient position (shown in FIG. 3) in which the fastener 36 isbeing moved from the shipping position to the installed position. Thethreaded portion 42 is temporarily retained within the retaining portion32 in a shipping position so that the module 10 may be shipped with thefasteners 36 to avoid variables leading to poor crash pulsetransmission, discussed above. The retaining portion 32 has threads 46that have a retaining portion minor diameter Z defined by the crest orpeak of the threads 46. The threaded portion 42 may be received in theretaining portion 32 by an interference fit or the base 20 may be moldedor cast about the threaded portion 42. If the base 20 is molded or castabout the threaded portion 42, the retaining material will be disposedwithin the retaining portion 32, which will prevent the fastener frombeing installed into the internally threaded member 16. Self-tappingthreads may be used to cut through the retaining material when movedfrom the shipping position to the installed position.

[0015] The present invention provides a fastener 36 with a threadedportion 42 having a minor diameter Y greater than the shaft diameter X.Similarly, the minor diameter Z of the retaining portion 32 will also begreater that the shaft diameter X. As a result, the shaft 38 will not bein an interference fit relationship with the retaining portion 32 sothat the compressive load of the fastener 36 alone secures the base 20to the vehicle mounting structure 14. Said another way, the minordiameter Z of the retaining portion 32 will not engage the shaft 38because the shaft diameter X is smaller that the minor diameter Z.

[0016] As discussed above, it is undesirable to have the threadedportion 42 engage both the base 20 and the internally threaded member16. Accordingly, it is preferable to have the threaded portion 42disposed outside of the retaining portion 32 when in the installedposition so that the threaded portion 42 only engages the internallythreaded member 16. In this manner, the threaded portion 42 will engageonly the internally threaded member 16 so that the base 20 is secured tothe vehicle mounting structure 14 by the compressive load of thefastener 36 alone. To this end, the present invention utilized afastener 36 that has a shaft length S greater that the retaining portiondepth R If the base 20 does not have a pocket 34 as shown in theFigures, then the shaft length S may need be the greater than the depthof the aperture 30.

[0017] The invention has been described in an illustrative manner, andit is to be understood that the terminology that has been used isintended to be in the nature of words of description rather than oflimitation. Obviously, many modifications and variations of the presentinvention are possible in light of the above teachings. It is,therefore, to be understood that within the scope of the appended claimsthe invention may be practiced otherwise than as specifically described.

What is claimed is:
 1. An air bag sensor module for a vehiclecomprising: a base having an aperture extending therethrough, saidaperture having a retaining portion; a sensor secured to said base forsensing vibrations caused by a crash of the vehicle; a fastener having ashaft with a head and a threaded portion opposite said head with saidthreaded portion temporarily retained within said retaining portion in ashipping position, said threaded portion having a minor diameter withsaid shaft portion having a shaft diameter less than said minordiameter.
 2. The module according to claim 1, wherein said retainingportion includes a depth and said shaft includes a length greater thatsaid depth.
 3. The module according to claim 1, wherein said threadedportion comprises self-tapping threads.
 4. The module according to claim3, wherein said base includes retaining material disposed within saidretaining portion, said self-tapping threads cutting through saidretaining material when moved from said shipping position to aninstalled position.
 5. The module according to claim 4, wherein saidbase is molded about said fastener.
 6. The module according to claim 5,wherein said base comprises plastic.
 7. The module according to claim 1,wherein said base comprises metal.
 8. The module according to claim 1,wherein said aperture includes a pocket adjacent to said retainingportion opposite said head, said threaded portion being disposed withinsaid pocket in a transient position.
 9. The module according to claim 1,wherein said retaining portion includes a retaining portion minordiameter greater than said shaft diameter.
 10. An air bag sensor modulefastening device for a vehicle comprising: a vehicle mounting structurehaving an internally threaded member; a base having an apertureextending therethrough and aligned with said internally threaded member,said aperture having a retaining portion; a sensor secured to said basefor sensing vibrations caused by a crash of the vehicle; a fastener forsecuring said base to said vehicle mounting structure, said fastenerhaving a shaft with a head and a threaded portion opposite said headwith said threaded portion temporarily retained within said retainingportion in a shipping position, and said threaded portion being disposedoutside of said retaining portion in an installed position in which saidthreaded portion is received in said internally threaded member tosecure said base to said vehicle mounting structure.
 11. The deviceaccording to claim 10, wherein said threaded portion includes a minordiameter with said shaft portion having a shaft diameter less than saidminor diameter.
 12. The device according to claim 10, wherein saidinternally threaded member comprises a nut secured to said vehiclemounting structure and aligned with a hole in said vehicle mountingstructure.
 13. The device according to claim 10, wherein said retainingportion includes a depth and said shaft includes a length greater thansaid depth.
 14. The device according to claim 10, wherein said threadedportion comprises self-tapping threads.
 15. The device according toclaim 14, wherein said base includes retaining material disposed withinsaid retaining portion, said self-tapping threads cutting through saidretaining material when moved from said shipping position to aninstalled position.
 16. The device according to claim 10, wherein saidaperture includes a pocket adjacent to said retaining portion oppositesaid head, said threaded portion being disposed within said pocket in atransient position.
 17. The device according to claim 10, wherein saidretaining portion includes a retaining portion minor diameter greaterthan said shaft diameter.